igneous
Granite Cobble
Granite
Hardness: 6-7 on Mohs scale. Color: Mottled pink, grey, and black. Luster: Dull to vitreous. Structure: Phaneritic (medium-grained crystalline). Composition: Quartz, alkali feldspar, and plagioclase.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, grey, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled pink, grey, and black. Luster: Dull to vitreous. Structure: Phaneritic (medium-grained crystalline). Composition: Quartz, alkali feldspar, and plagioclase.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). This specific specimen has been rounded into a 'cobble' or 'river rock' shape by water erosion or glacial transport over thousands of years.
Uses & applications
Used in construction, aggregate, landscaping, and as a decorative stone. High-quality slabs are used for countertops.
Geological facts
Granite makes up much of the Earth's continental crust. It is one of the hardest and most durable common rocks, which is why it is used for monuments.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. Common in mountain ranges and riverbeds. This rounded shape indicates it has traveled far from its source.
